import pandas as pd
class BIAS:#Wide
    def __init__(self,size=100):
        self.size=size
    def oncalc(self,a,b,timekey=None):
        d=None
        if not pd.isna(a):
            if not pd.isna(b):
                if b!=0:
                    d=self.size*(a-b)/b
        return d